Population Growth Of Yeast And Effects Of Various Substrates On This Population Growth

Population Growth Of Yeast And Effects Of Various Substrates On This

Population Growth

Plan: 1. Introduction;

Yeast is a unicellular fungus which reproduces asexually by budding or

division, as in the case of the genus Saccharomyces, which is

important in fermentation in food (walker, 1998). Yeasts are widely

distributed in nature.

Like bacteria and moulds, they can have beneficial and non-beneficial

properties in food production. The most well known examples of yeast

fermentation are in the production of alcoholic drinks and the

leavening of bread. Although there is a large range of species of

yeasts, only a few species are used in the food industry. These

species are usually either Ascomycetous yeasts or yeasts that belong

to the genus Candida. Unlike most Fungi yeast cells are round or oval

in shape.

2. Aim-

The aim of the investigation is to discover whether different

substrates of carbohydrates have a direct effect on the population

growth of yeast cells. This will be done by direct counting of cells

by haemocytometer to discover the average count of cells. This process

shall be over a time period of 5 days.

3. Method-

Apparatus required;

* For the yeast culture ;

* 6g of dried active bakers yeast ;

* 6 sugars (enough for 6 yeast cultures) in this investigation the

sugars used were:

* Glucose, Fructose, Dextrin, Ribose, Galactose and Sucrose;

* 600 ml of Distilled water;

* 6 Conical flasks with air blocks (in this instance cotton wool

with suffice);

* Compound microscope with lamp;

* Water bath set at constant 37ºC;

* Haemocytometer;

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...nting chamber of the Haemocytometer is 0.1 mm deep. The central

squared area is divided into 25 main squares, each of which is

subdivided into 16 smaller squares. The volume of suspension above the

smallest squares is a uniform 0.00025 mm³. So the the number of cells

in the culture suspension is given by:

D*N

S*C

Where D= dilution of original culture

N= total number of cells counted

S= number of squares counted

C= volume of 1square

The experiment is taken over 5 days, and every 24 hours a reading is

taken. Raw results will be tabulated first, with headings of sample

time and cell count. This shall be done for all 6 samples. The

findings will then be processed to find an average cell count per day.

A graph will be drawn of cell count against time in hope that a growth

curve will be achieved